The San Francisco forktail damselfly thrives in the city's signature cool, dense fog

Nature · Published 29 September 2026 · Updated 25 October 2026 Swipe more like this →

In short: While most damselflies chase the sun, the San Francisco forktail prefers the city's chilly, misty air. These rare insects have evolved darker, sturdier bodies to survive in their unique urban habitat. When they mate, they form a distinct heart shape and fly in tandem for over an hour.

The San Francisco forktail damselfly is a biological outlier within the odonate family, which includes both damselflies and dragonflies. While its relatives generally favor sunny environments, this species has adapted to the specific, foggy conditions of San Francisco. This adaptation includes a darker, more robust physical structure and a higher tolerance for cold, allowing it to occupy a niche that few other insects can handle. Despite this specialization, it is currently recognized as one of the rarest damselfly species in North America.

Life for this insect is increasingly precarious. The species faces significant threats from habitat loss and the ongoing effects of climate change, which is reducing the frequency of the cool fog it relies upon. Furthermore, the forktail is susceptible to hybridization with other local species, which complicates conservation efforts. To combat these pressures, a collaborative project involving scientists from the San Francisco Zoo and ecologists from the Presidio Trust is currently working to re-establish the population within the city.

Distinguishing the forktail from its dragonfly cousins involves observing subtle anatomical differences. Damselflies are generally more slender, and when resting, they fold their wings neatly behind their bodies, whereas dragonflies keep their wings outstretched. Additionally, damselfly eyes are spaced apart, unlike the larger, connected eyes of dragonflies. Like all odonates, the forktail begins life as an aquatic nymph, or naiad, breathing through caudal gills. This underwater phase can last anywhere from two months to over a year, depending on environmental factors like food availability and water temperature.

As adults, these insects serve as vital predators, feeding on mosquitoes, flies, and other small insects. By ambushing prey among low vegetation and grasses, they play an essential role in the local food web. Their mating behavior is particularly striking, as they link their bodies into a heart shape before embarking on a prolonged tandem flight, a display that highlights the unique character of this rare urban inhabitant.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Damselflies fold slim wings while dragonflies usually don’t
• Dragonflies and damselflies are both expert hunters, but they dominate very different environments.
• Why these common dragonflies are named after a carpenter’s leveling tool
• The emperor dragonfly is a territorial giant currently conquering the cooling northern latitudes
• Some fireflies use romantic light signals to lure and devour their own kind
• Which unusual creatures would David Attenborough choose for his personal ark?
• Why are bear sightings becoming a common occurrence in our backyards and city streets?
• Can we restore the lost reindeer of the Scottish Highlands?
• The hairy, elusive Sumatran rhino is vanishing from the wild
• How tracking bluefin tuna could reshape ocean management and harvesting
• The elusive Gobi bear was once considered nothing more than a myth
• High-tech tracking reveals the secrets of the Galapagos tortoise

More in Conservation · More in Nature · Latest · A–Z · All topics